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🧬 JavaScript Advanced Data Types – Arrays, Maps, Sets & More (2025 Guide)

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🧲 Introduction – Why Learn Advanced JavaScript Data Types?

In modern JavaScript, mastering advanced data types like Arrays, Maps, Sets, and newer structures like Symbols, Typed Arrays, and Weak Collections is crucial for performance, memory efficiency, and building scalable applications.

🎯 In this guide, you’ll learn:

• How to use Arrays, Sets, Maps, Typed Arrays, WeakMap, WeakSet, and Symbols
• Powerful array methods for searching, sorting, and iterating
• How Reflect and DataView expand JS’s capabilities for meta-programming and binary data

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📘 Topics Covered

🔢 Topic	📄 Description
Arrays / Sets / Maps	Core structured data types
Typed Arrays / WeakMap / WeakSet	Advanced memory-efficient collections
Array Methods	Search, sort, iterate
Set & Map Methods	Add, delete, check, iterate
Symbol	Unique property keys
Reflect	Meta-level operations
DataView	Low-level memory access

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🧮 JavaScript — Arrays, Sets, Maps, Typed Arrays, WeakMap, WeakSet

🔸 Arrays

An Array holds an ordered list of values.

const fruits = ["apple", "banana", "cherry"];
console.log(fruits[1]); // banana

🔸 Sets

A Set stores unique values.

const ids = new Set([1, 2, 2, 3]);
console.log(ids); // Set {1, 2, 3}

🔸 Maps

Map stores key-value pairs and maintains insertion order.

const scores = new Map();
scores.set("Alice", 90);
console.log(scores.get("Alice")); // 90

🔸 Typed Arrays

Efficiently handle binary data.

const buffer = new ArrayBuffer(8);
const intView = new Int32Array(buffer);
intView[0] = 42;
console.log(intView[0]); // 42

🔸 WeakMap / WeakSet

Memory-managed collections for objects.

const wm = new WeakMap();
const obj = {};
wm.set(obj, "data");
// obj must be an object; key is weakly held

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🧰 JavaScript — Array Methods (Search, Sort, Iterate)

🔍 Search Methods

const nums = [10, 20, 30];
nums.includes(20);   // true
nums.indexOf(30);    // 2

🔃 Iterate with forEach, map, filter

nums.forEach(n => console.log(n));
const doubled = nums.map(n => n * 2);
const filtered = nums.filter(n => n > 15);

🔢 Sorting Arrays

const names = ["Zoe", "Adam", "Bob"];
names.sort(); // ["Adam", "Bob", "Zoe"]

Custom sorting:

const prices = [100, 25, 300];
prices.sort((a, b) => a - b); // [25, 100, 300]

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📊 JavaScript — Set & Map Methods

🔹 Set Methods

const tags = new Set();
tags.add("html");
tags.add("css");
tags.has("css");    // true
tags.delete("css"); // removes "css"

🔹 Map Methods

const capital = new Map();
capital.set("France", "Paris");
capital.has("France");       // true
capital.delete("France");    // removes entry

Use for...of to loop through Sets or Maps:

for (let [key, value] of capital) {
  console.log(`${key}: ${value}`);
}

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🧿 JavaScript — Symbol

Symbols are unique and immutable identifiers.

const sym1 = Symbol("id");
const sym2 = Symbol("id");
console.log(sym1 === sym2); // false

Used for private object properties:

const uid = Symbol("uid");
const user = {
  name: "John",
  [uid]: 12345
};

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🪞 JavaScript — Reflect

The Reflect API provides methods for interacting with object properties.

const user = { name: "Alice" };
Reflect.set(user, "age", 30);
console.log(Reflect.get(user, "age")); // 30

Useful in meta-programming and proxies.

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📐 JavaScript — DataView

DataView lets you manipulate individual bytes of an ArrayBuffer.

const buf = new ArrayBuffer(2);
const view = new DataView(buf);
view.setUint8(0, 255);
console.log(view.getUint8(0)); // 255

Used in:

• Binary file processing
• WebGL / game engines
• Device data interpretation

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📌 Summary – Recap & Next Steps

Advanced data types in JavaScript provide robust ways to handle collections, meta-level operations, and memory-efficient data access. Mastering these enhances your JS proficiency and prepares you for building complex systems.

🔍 Key Takeaways:

• Use Sets/Maps for uniqueness and key-value storage
• Typed Arrays/DataView handle binary data efficiently
• Symbols and Reflect provide tools for meta-programming
• Array methods make manipulation intuitive and powerful

⚙️ Real-World Relevance:
These types are heavily used in frameworks, backend tools (like Node.js), browser APIs, and memory-critical environments.

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❓ FAQs

Q1: When should I use a Set instead of an Array?

✅ When you need to store unique values without duplicates.

Q2: What are Typed Arrays used for?

✅ Typed Arrays offer fast binary data access, often in games, graphics, or buffer handling.

Q3: Can Maps use objects as keys?

✅ Yes. Unlike objects, Maps can have objects or functions as keys.

Q4: What is the purpose of Symbols?

✅ To create unique property keys, especially for private or hidden object members.

Q5: How is Reflect different from Object methods?

✅ Reflect methods are functional (like Reflect.set) and align well with proxies for meta-programming.

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